Brigham and Women's has discovered that more women are choosing unnecessary mastectomies due to misinformation.

The Boston area does a good job of spreading awareness and providing support for breast cancer patients, from specialized yoga studios, to foundations who raise millions of dollars a year, to annual fundraising 5k runs. But researchers at the cancer center at Brigham and Women’s Hospital have a different kind of campaign in mind; one that’s less about awareness and more focused on education about the details of the disease.

In a new study published in the journal Annals of Internal Medicine, researchers from Brigham and Women’s and the Dana Farber Cancer Institute found that an increasing number of women who are diagnosed with cancer in only one breast are opting to have double mastectomies.

Researchers conducted a survey of 550 women age 40 and younger who had undergone a contralateral prophylactic mastectomy (CPM)—which is the surgical removal of both breasts—in the last two years. The survey consisted of 23 questions about the decision making process regarding the surgery, the risk perception, and future breast cancer worry. Of the 550 who had both breasts removed, 123 of them did not have cancer in both breasts.

Almost 100 percent of participants said that increasing their chance of survival and decreasing their chance of contracting cancer in the other breast was the main reason for deciding to have the surgery. Participants who did not inherit cancerous genetic mutations estimated that 10 in every 100 women will develop cancer in both breasts after one has been diagnosed, but in reality, the chances of that happening is closer to 2 percent, researchers say. Patients who did inherit mutation in the BRCA1 and BRCA2 genes which can lead to cancer, more accurately estimated their risk for cancer in both breasts.

The study suggests that women are overestimating the chances of developing cancer in the other breast and making big decisions without being fully informed of the actual risk.

Dr. Shoshana Rosenberg, of the Dana Farber/Brigham and Women’s Cancer Center, and lead author of the study said in a report:

“Our findings underscore how important it is that doctors effectively communicate the risks and benefits of CPM to women. We need to be sure that women are making informed decisions, supported decisions, based on an accurate understanding of the pros and cons of the procedure, and in a setting where anxiety and concerns can be addressed.”